A conventional sheet processing unit can take out sheets from piled sheets one by one and convey the taken sheets one by one. The taken sheets can be processed (tested) and classified into the sheets for recycling or the sheets for discharging.
The conventional sheet processing unit comprises: a taking part for taking the sheets, a conveying part for conveying the taken sheets, a testing part for testing the conveyed sheets, a classifying part for classifying the sheets on the basis of the result of the testing, and a collecting part for collecting the classified sheets respectively.
The conventional sheet processing unit operates as follows. Collected sheets are conveyed into the unit as piled sheets. The piled sheets consist of n (desired number) sheets. The taking part takes out the sheets one by one from the piled sheets at regular intervals in succession. Then, the conveying part conveys the taken sheet at a high speed by using a belt mechanism. The testing part tests whether each of the conveyed sheets has any damage respectively, that is, whether each of them should be recycled or discharged. Then, the classifying part classifies and guides the tested sheets into two ways respectively. The guided sheets are collected as sheets for recycling or as sheets for discharging respectively. Additional classifying parts can be arranged in the sheet processing unit.
The collected sheets as the sheets for discharging are then processed by a shredder or the like. The speed of the sheet processing is constant at several decade sheets per second. The conveying speed is constant at several meters per second. A typical conventional sheet processing unit is explained with reference to FIGS. 23 and 24.
FIG. 23 schematically shows the construction of the typical conventional sheet processing unit. FIG. 24 is an enlarged view of a portion including a taking part of the conventional sheet processing unit. The conventional sheet processing unit 100 comprises: sheets 101, a taking part 102 for taking the sheets, a conveying part 103 for conveying the taken sheets, a testing part 104 for testing the conveyed sheets, a classifying part 105 for classifying the sheets on the basis of the result of the testing, and a collecting part 106 for collecting the classified sheets respectively. These parts 102 to 106 are arranged in order of the reference numbers. The taking part 102 has a sheet supplying unit 110, a taking unit 111 and a double-taking preventing unit 113.
The sheets 101 are conveyed to the sheet supplying unit 110 by a conveying unit (not shown) as piled sheets. The piled sheets have n (desired number) sheets. The sheets 101 are taken one by one at regular intervals successively by the sheet supplying unit 110 and the taking unit 111. Then, the taken sheets are supplied to a conveying way 112. The double-taking preventing unit 113, which is arranged at a distance from the taking unit 111, prevents two or more sheets from being taken at one time. The testing unit part 104 is arranged above the sheets conveyed on the conveying way 112 that is formed backward (right in FIG. 18, downward of the sheet conveying direction) with respect to the taking unit 111. The testing unit 104 tests a surface state (damaged state, soiled state) of each of the sheets 101, which are conveyed one by one.
The collecting part 106 has a portion for collecting sheets that should be recycled and a portion for collecting sheets that should be discharged. The sheets are classified by the result of testing with the testing unit 104, and guided into the portion for collecting sheets that should be recycled and the portion for collecting sheets that should be discharged, respectively. The respective guiding of the classified sheets is carried out by a facing-type gate unit 115 arranged on the conveying way 112.
The collecting part 106 has also wheels with fins 117. The wheels with fins 117 are adapted to receive and stop the sheets that are conveyed at a high speed. Then, the stopped sheets 101 fall and pile up again. The wheel 117 is roller-like, and the fins of the wheel 117 form spiral grooves around the center of the wheels 117. The wheels with fins are driven by a stepping motor or the like. The sheets that should be recycled are conveyed out from the sheet processing unit as piled sheets which consist of desired number of sheets. The sheets that should be discharged are conveyed to the discharging process.
Photoelectric sensors 119 are arranged at desired positions on the conveying way 112 for detecting a passage of each of the sheets 101. For simplicity, only one sensor 119 is shown in drawings. The photoelectric sensors 119 are also used for detecting timings of taking the sheets 101, intervals thereof and a jammed state (sheet-staffed state). The sensors 119 are also used to confirm guiding state of the sheets 101 into the collecting part 106 and to calculate intervals of the guiding. In addition, one of the photoelectric sensors 119, which is disposed just behind the taking unit 111, is used to detect intervals of the sheets just after taken and/or skews of the sheets just after taken.
The taking part 102 of the sheet processing unit is explained in more detail as below, with reference to the FIG. 24.
The taking part 102 has a sheet supplying unit 110, a vacuum-absorption type of taking unit 111 and a double-taking preventing unit 113.
The vacuum-absorption type of taking unit 111 has a vacuum chamber 121 with an opening. The inside of the chamber 121 can be maintained at a pressure lower than the atmospheric pressure. A thin cylindrical rotor 122 is disposed around the chamber 121, and is adapted to rotate around the same. Some holes are provided with the rotor 122. A plain belt 123 supplies a driven force to the rotor 122. The plain belt 123 also serves as a member of the conveying way 112.
The opening of the vacuum chamber 121 is arranged at an opposite position to sheets piled on the sheet supplying unit 110. When the rotor 122 rotates and the holes of the rotor 122 come above the opening of the chamber 121, a vacuum absorption force appears. An absorption part herein means a surface formed by the holes at that time. In addition, an open-close controller such as an electromagnetic valve (not shown) is disposed in a tube or the like connecting the vacuum chamber 121 and a suction unit such as a vacuum pump (not shown). Thus, the pressure in the vacuum chamber 121 can be controlled.
The sheet supplying unit 110 has: a sheet stage 124 for supporting greater parts of the sheets 101, a linear motor 125 fixed to the sheet stage 124 for generating a desired force, a lever 126 moved relatively with respect to the sheet stage 124 by the linear motor 125, and a position sensor 127 fixed to the sheet stage 124 for detecting the position of the lever 126.
The position sensor 127 is for example a non-contact type of displacement meter. The sheet stage 124 is connected to an actuator for driving via a transmitting mechanism such as a ball-screw (not shown). The actuator for driving is controlled by a controlling unit (not shown) on the basis of the value of the position sensor 127.
As shown in FIG. 2, the double-taking preventing unit 113 has a chamber whose inside can be maintained at a pressure lower than the atmospheric pressure. The unit 113 also has a surface facing to the rotor 122 and having such a curvature that the surface is along the rotor 122 at a distance. The surface has some holes to the inside of the chamber. Then, the sheet passing between the rotor 122 and the double-taking preventing unit 113 can be absorbed and stopped.
The operation of taking of the sheets is explained as below.
A desired electric current is given to the linear motor 125 to generate a desired driving force which moves the lever 126 upward. When the sheet stage 124 moves toward the taking unit 111, the sheet of the top of the piled sheets becomes in contact with the absorption part of the rotor 122, and is pressed to the absorption part thereof. A downward force to the lever 126 is generated by the press. If the downward force becomes not less than the driving force, the lever 126 starts to move downward. Then, the position sensor 127 measures the position of the lever 126 i.e. the displacement thereof relative to the sheet stage 124. When the positioning of the sheet stage 124 is carried out in such a manner that the measured value is a predetermined value or within a predetermined range, the sheet 101 and the rotor 122 are pressed to each other with a pressure of a predetermined value or in a predetermined range.
Thus, the controlling unit (not shown) positions the sheet stage 124 in such a manner that the measured value of the position of the lever 126 is the predetermined value or within the predetermined range.
When the measured value becomes the value or within the predetermined range, the open-close unit such as a electromagnetic valve (not shown), which has been closed till then, is opened to enable the sheets to be taken. At that time, airflow can be jetted from a nozzle or the like to a not-pressed portion (right portion in FIG. 18) of the sheets to promote to separate the sheets. The double-taking preventing unit 113 prevents a not-targeted sheet from being taken when a targeted sheet is taken.
As described above, the sheet processing unit employs a press-type sheet supplying, in which the sheet 101 are pressed to the taking rotor 122. Thus, the sheet 101 and the absorption part of the taking rotor 122 are assured to become in good contact with each other. Thus, the absorption force of the taking rotor 122 is efficiently transmitted to the sheet 101 to make the taking operation stable. In the case, a contacting state between the absorption part of the rotor 122 and the sheet 101, and a force transmitting state are detected as the pressing force while the sheet 101 is taken.
Recently, improvement of the performance of the sheet processing unit is requested. Especially, further improvement of the processing speed and the taking accuracy is requested.
However, the above conventional sheet processing unit has a problem that the taking accuracy becomes worse when the large number of the sheets are set on the sheet stage. The conventional sheet processing unit also has a problem that the taking accuracy becomes worse depending on the kind or the state of the sheets. In addition, the conventional sheet processing unit has such a complex sheet supplying unit that the sufficient intervals are necessary for the taken sheets. That is, the conventional sheet processing unit has a difficulty for the successive taking.